Pesticides increase risk of Parkinson's

Exposure to pesticides, even in small amounts, can lead to an increase in Parkinson's disease, according to a scientific study published Wednesday.

Research on nearly 1000 Parkinson's sufferers in five countries -- one of the largest such studies to date -- showed that high-level exposure upped the risk of contracting the debilitating brain disease by 39 percent.

Lower-level exposure, consistent with hobby-gardening use of pesticides, corresponded with a nine-percent increase, said Finlay Dick, the lead author of the study, published in the British journal Occupational and Environmental Medicine.
Parkinson's is an incurable, degenerative disease of the central nervous system that causes uncontrollable shaking, along with impaired speech and movement. In approximately one third of cases it also results in dementia.

Estimates of its prevalence vary between 0.1 and 0.3 percent of the population, said Dick, meaning that approximately one in 500 people contract the disease.

Previous studies have also established a clear link between Parkinson's and pesticides, with a major survey in the United States among agricultural workers last year reporting an even higher risk, at some 70 percent.

But the research by Dick and his colleagues at Aberdeen University provides far more detailed information about how and when -- and to what extent -- exposure occurred.

Using British occupational safety limits as a standard, the researchers divided the respondents into two groups based on the intensity and duration of exposure.

The 959 respondents were questioned about lifetime exposure to pesticides and a variety of other chemicals, as well as other potential factors that may contribute to the illness, such as incidence within the family and head injuries.

"The biggest risk was family history," Dick told AFP. A parent or sibling with Parkinson's increased the risk by a factor of three.

Not surprisingly, farm workers in the five regions examined -- in Scotland, Sweden, Romania, Italy and Malta -- were the occupational group showing the highest link between pesticide use and Parkinson's.

Dick emphasized that an increased risk factor does not mean that anyone who has used pesticides is now in danger of contracting it.

"The key message here is that just under half of those interviewed" -- including an additional 1989 people in a control group -- "reported some use of pesticides," he said. "The vast majority of people who used them will never have Parkinson's."

Genetic factors and being knocked unconscious also showed a significant link with the onset of the disease, according to the study. The link with pesticide "is another piece in the jigsaw," Dick said.

Interestingly, tobacco use offered a clear measure of protection against the disease.